It is not the best Makefile but it does the job. If you placed your SDK into another path, just edit the PALMINC-Variable in this Makefile.
Make sure you use the correct filename. If you have a helloWorld-Application liks this:

and the c-file is called "HelloWorld.c", you can use it as it is. Otherwise just change the filename.

Copy the Makefile in folder next to your .c-file and run in a terminal "make all". You should now have a working .prc-file, which you can install on a Palm-OS-Device or POSE:

Note: This is a very basic not the best way to compile and build Palm-OS-Applications. If you are lucky and own a copy of CodeWarrior for Palm Os, use this IDE. It comes with everything you need and generates much better code. And it runs with Wine on Ubuntu without any problems.